The Application Of Redox Electrolyte For PANI/SnO₂Supercapacitor

Supercapacitor was developed as a specialized energy storage device in recentdecades. Energy conservation and environmental protection are its two significantadvantages, so that it will be of concern in the field of electrochemistry in the future.In this thesis, SnO2was gained based on the hydrothermal method, and then thePANI/SnO2composite materials were made by chemical oxidation polymerization.The properties of the materials were obtained by scanning electron microscope (SEM),Fourier transform infrared spectroscopy (FTIR), X-ray diffraction analysis (XRD),galvanostatic charge-discharge (GCD), cyclic voltammetry (CV), and electrochemicalimpedance spectroscopy techniques (EIS). Besides, introducing hydroquinone (HQ)and Fe3+/Fe2+ion pair as redox mediators into1mol L-1H2SO4formed ahigh-property redox electrolytes for PANI/SnO2supercapacitors. The main contentsobtained are as follow:1. SnO2was gained based on the hydrothermal method, and then the PANI/SnO2composite particles were made by chemical oxidation polymerization. The specificcapacitance of PANI/SnO2composite was430F g-1with specific energy density of53.8Wh kg-1at power density of252.8W kg-1in1mol L-1H2SO4electrolyte. Thesevalues were at least four times higher than the corresponding values of SnO2. After2000cycles, the capacitance retention of85.6%was observed.2. Introducing HQ as redox mediators into1moL L-1H2SO4electrolyte formedthe novel redox electrolytes for PANI/SnO2supercapacitors. In this novel electrolyte,the specific capacitance of PANI/SnO2supercapacitor was heightened by297F g-1,reaching727F g-1. The power density of this PANI/SnO2supercapacitor is255Wkg-1when the energy density is90.9Wh kg1. Meanwhile, increasing theconcentration of HQ increased the capacitance of the PANI/SnO2supercapacitors. Inaddition, the supercapacitor showed good stability with retention of the initialcapacitance values of81.2%after2000galvanostatic cycles.3. The influences of a redox electrolyte based on different Fe3+/Fe2+ion pairconcentration in1mol L-1H2SO4solution on the pseudocapacitive behaviors ofPANI/SnO2supercapacitor were investigated. It is discovered that the specificcapacitance of the supercapacitor increase firstly and then decrease with increasingthe Fe3+/Fe2+ion pair concentration. The performance of the supercapacitor was thebest when the Fe3+/Fe2+concentration was0.4mol L-1. The capacitance of PANI/SnO2 supercapacitor is doubled compared with the undoping Fe3+/Fe2+ion pair ones and itreaches to1172F g-1. Simultaneously, the energy density of this supercapacitor is142.8Wh kg-1at the power density of487.1W kg-1, both of which are enhancedtremendously. Furthermore, it could be inferred that the PANI/SnO2supercapacitorreflected outstanding cyclic atability with retention of the initial capacitance values of91.8%after2000galvanostatic cycles.In the new redox electrolyte system, the capacitance of supercapacitor combinestwo parts: the capacitance of PANI/SnO2electrode material and the pseudocapacitivecontributions of reversible redox process of the redox active mediators. Therefore, theelectrochemical properties of supercapacitors are improved greatly.